Where are you seeing on the W-2 that the sick pay was taxed at a higher rate?
If your employer paid for the policy then the amount would be included in box 1 of the W-2 and taxed at the same rate as the rest of your wages.
See this TurboTax support FAQ for sick pay - https://ttlc.intuit.com/turbotax-support/en-us/help-article/income/third-party-sick-pay-taxable/L1AE...
